In a semiconductor integrated circuit device, a silicon nitride film has been widely used as a material of an etching stopper, a side wall spacer, a stress liner or the like, as well as as an insulating material of a gate insulating film. In the related art, there are known methods of forming such a silicon nitride film.
There is a first conventional method of forming a silicon nitride film (SiBN film) containing boron (B) as a ternary thin film. In the first conventional method, dichlorosilane (DCS: SiH2Cl2) is used as a silicon source gas and boron trichloride (BCl3) is used as a boron source gas. Also, the first conventional method includes:
(1) simultaneously supplying the DCS gas and the BCl3 gas into a processing chamber to form a boron-containing silicon film;
(2) purging the interior of the processing chamber;
(3) supplying ammonia (NH3) as a nitriding gas into the processing chamber such that the boron-containing silicon film is nitrided to be changed to plasma, thereby forming the SiBN film; and
(4) purging the interior of the processing chamber.
By repeating the processes of (1) to (4), the SiBN film is formed on a surface to be processed of a target object.
The SiBN film formed as above provides the following effects:
a) Better step coverage than that formed using a plasma enhanced chemical vapor deposition (PECVD);
b) A reactive ion etching (RIE)-based etching, that is easier than a typical silicon nitride film (SiNx film) or a typical boron nitride film (BN film);                Better wet etching resistance than the typical boron nitride film (BN film); and        Lower relative dielectric constant than the typical SiNx film.        
Further, there is a second conventional method for forming a boron-containing silicon nitride film (SiBN). In the second method, like the first conventional method, DCS is used as a silicon source gas and BCl3 is used as a boron source gas. The second conventional method includes:
(1) supplying the DCS gas into a processing chamber to form a silicon film;
(2) purging the interior of the processing chamber;
(3) supplying NH3 as a nitriding gas into the processing chamber such that the silicon film is nitrided or is changed to plasma, thereby forming the silicon nitride film;
(4) purging the interior of the processing chamber;
(5) supplying BCl3 as the boron source gas into the processing chamber to add boron to the silicon nitride film, thereby forming the SiBN film;
(6) purging the interior of the processing chamber;
(7) supplying NH3 as a nitriding gas into the processing chamber such that the boron-containing silicon nitride film is further nitrided by NH3 activated by plasma and a residual Cl component derived from the BCl3 gas is removed from an SiBN film; and
(8) purging the interior of the processing chamber.
By repeating the processes of (1) to (8), the SiBN film is formed on a surface to be processed of a target object.
The SiBN film formed as above provides the following effects:                Better etching resistance by the NH3 activated by plasma, compared with a case where the silicon nitride film is not further plasma-nitirided; and        Lower relative dielectric constant than a typical SiNx film.        
In the second method, diborane (B2H6) and trimethylboron (B(CH3)3) containing no halogen element, may be used as the boron source gas, in addition to the BCl3 gas.
Also, there is a third conventional method of forming a boron-containing silicon film (SiBN). In the third conventional method, monosilane (SiH4) is used as the silicon source gas and BCl3 is used as the boron source gas. In the third conventional method includes:
(1) supplying an SiH4 gas into a processing chamber to form a silicon film;
(2) purging the interior of the processing chamber;
(3) supplying the BCl3 gas into the processing chamber such that boron is adsorbed onto a surface of the silicon film, thereby forming the boron-containing silicon film; and
(4) purging the interior of the processing chamber.
By repeating the processes of (1) to (4), the boron-containing silicon film is formed on a surface to be processed of a target object.
The boron-containing silicon film formed as above provides the following effects:                The silicon film can be formed at lower temperature (e.g., about 350 degrees C.) due to the boron atom acting as a catalyst, compared with the formation of a silicon film using the SiH4 gas alone; and        It is obtained good step coverage even at the lower temperature.        
Also, in the third conventional method, a B2H6 gas containing no halogen element may be used as the boron source gas, in addition to the BCl3 gas.
Recently, user's demand for a film forming apparatus has been impressively changed. Such a demand includes “enhancement of productivity of the film forming apparatus.” The enhancement of productivity defines maintaining and enhancing the better step coverage, achieving the electrical and physical characteristics required for thin films, and obtaining both the better processability and the better etching resistance, which are imposed on the first and second conventional methods.
So far, the enhancement of productivity has mainly been focused on improving so-called hardware, such as an increase in speed of a transfer robot, an increase in control speed of a temperature in a heating device or a cooling device, and the like. Unfortunately, in recent years, the hardware improvement alone makes it difficult to meet the user's demand for productivity.